>Psychtoolbox>PsychGamma

[fit_out,x,fitComment] = …
FitGamma(values_in,measurements,values_out,[fitType])

Fit a gamma function. This essentially a driver function.
It has two main purposes.

First it tries several different
underlying parametric forms for the fit and chooses the best
for a particular data set.

Second, it does the bookkeeping for fitting each column of
input measurements. (Each of the underlying fit functions expects
only vector input.)

To a large extent, the interface to the underlying fit functions
(e.g. FitGammaPow, FitGammaSig, …) is uniform. However, this routine
does have to know a little bit about initial value dimension and choice.
We have tried to localize this information in the initialization routines
(e.g. InitialXPow, InitialXSig, …) as much as possible, but some
caution is advised.

Optional argument fitType allows you to force the return of a particular
parametric form. Currently:
fitType == 1: Power function
fitType == 2: Extended power function
fitType == 3: Sigmoid
fitType == 4: Weibull
fitType == 5: Modified polynomial
fitType == 6: Linear interpolation
fitType == 7: Cubic spline

All fit types are in a form such that the fit is forced through the
origin for 0 input. This is because our convention is that gamma
correction happens after subtraction of the ambient light.

NOTE: FitGammaPow (and perhaps other subroutines) uses CONSTR, which is part of the
Mathworks Optimization Toolbox.

Also see FitGammaDemo.